Employee Benefit Plans (AOCI and regulatory assets and liabilities that have not been recognized as components of periodic benefit (credit) cost) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ (324)		$ (877)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	1,709		2,865
Prior service (credit) cost	10		11
Total	1,719	[1]	2,876	[1]
Related expenses	1,700		2,900
Amount included in AOCI	1,000		1,800
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(40)		229
Prior service (credit) cost	(271)		(71)
Total	(311)	[1]	158	[1]
Related expenses	(311)		158
Amount included in AOCI	$ (156)		$ 69

[1] As of December 31, 2013, of the $1.7 billion and $(311) million related to pension benefits and other postretirement benefits, $1.0 billion and $(156) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities. As of December 31, 2012, of the $2.9 billion and $158 million related to pension benefits and other postretirement benefits, $1.8 billion and $69 million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities.